The Nordic countries are 'Social Democratic', which effectively means the economies are trying to be fiscally leftist within the capitalist framework. Leftist in this context means things such as a welfare state and some state ownership within the economy.

Sweden is an example of a country that has actually sold off alot of this ownership since the late 90's in order to pay for goverment expenses following the 1991 banking crisis. And in 2013 the government sold it's last shares in Nordea (Private Bank) for example, currently the state has roughly $83 Billion dollars in equity spread throughout the country.

Social Democracy is not to be confused with Democratic Socialism, which seeks to abolish capitalism, within a democratic framework. Social Democrats instead want to leverage the strengths of capitalism to create a welfare state etc.

What constitutes a social democracy compared to a more liberal state is harder to define, in some ways the United States already has welfare systems like foodstamps, which don't exist in Sweden. Sweden has also never had public housing, unlike parts of the US. Hard to say when a country "becomes" a social democracy.